Digital frequency meter design based MCU 51

1, the specific function

Collection and analysis of operating frequency through the microcontroller 52, in a program to be displayed on the LCD screen LCD1602, through the LCD screen, allowing users to visually see the current input frequency is.

2, design ideas

(1) can measure the frequency of the sine wave, triangular wave or a square wave.

(2) measuring the frequency range of 1Hz-20MHz, and can detect a minimum value of the amplitude of the signal 1Vpp;

(3) detected by the display LCD LCD1602 instant frequency value (up to eight digits, the unit is Hz).

 Hardware:

3, part of the code

#include <reg52.h>
unsigned long int fre; 
unsigned char time;
unsigned int count;
unsigned int count1;
sbit   LCD_RS=P1^0;	  //片选信号 
sbit   LCD_RW=P1^1;	  //读写信号 
sbit   LCD_E=P1^2; 	  //使能信号 
#define LCD_DB  P0	//数据信号 
unsigned char character[10]={0};//在屏幕上显示的字符串 
unsigned char character_1[]={"fre= Hz"};
unsigned char FLAG = 0;  //是否分频选择标志
void LCD_init(void);//初始化函数   
void LCD_write_command(unsigned char command);//写指令函数	 
void LCD_write_data(unsigned char dat);//写数据函数	   
void LCD_disp_char(unsigned char x,unsigned char y,unsigned char dat);//在某个屏幕位置上显示一个字符,X（0-15),y(1-2)
void delay_n40us(unsigned int n);//延时函数
void timer_init();            //中断初始化函数  
//-----------------------------延时函数---------------------------
void delay_n40us(unsigned int n)		  //延时函数 
{
	unsigned int i;
	unsigned char j;            
	for(i=n;i>0;i--)
	for(j=0;j<2;j++);          
} 
void delay_1s()
{
	unsigned int i,j;
	for(i = 0;i<100;i++)
		for(j = 0;j<1000;j++);
} 
//---------------------lcd1602液晶显示函数--------------------                                     
void LCD_init(void)	 //液晶初始化函数 
{
	LCD_write_command(0x38);//设置8位格式，2行，5x7
	LCD_write_command(0x38);//设置8位格式，2行，5x7
	LCD_write_command(0x38);//设置8位格式，2行，5x7
	LCD_write_command(0x0c);//整体显示，关光标，不闪烁 
	LCD_write_command(0x06);//设定输入方式，增量不移位
	LCD_write_command(0x01);//清除屏幕显示	  
	delay_n40us(100);//清屏延时 
} 
void LCD_write_command(unsigned char dat)  //写命令函数 
{
	LCD_DB=dat;
	LCD_RS=0;//指令	 
	LCD_RW=0;//写入	 
	LCD_E=1; //使能 	 
	LCD_E=0;
	delay_n40us(1);//写命令延时   
}	 
void LCD_write_data(unsigned char dat)	  //写数据函数 
{
	LCD_DB=dat;
	LCD_RS=1;//数据	  
	LCD_RW=0;//写入	  
	LCD_E=1;//使能  
	LCD_E=0;
	delay_n40us(1);	 //写数据延时 
}
void LCD_disp_char(unsigned char x,unsigned char y,unsigned char dat)//显示一个字符 
{
	unsigned char address;
	if(y==1)
	         address=0x80+x;	 //显示在第一排的时候的x的地址 
	else
	         address=0xc0+x;	 //显示在第二排的时候的x的地址 
	LCD_write_command(address);	 //输入地址 
	LCD_write_data(dat);		 //输入数据 
}
void LCD_disp_num(unsigned char x,unsigned char y,unsigned char dat)//显示一个数字
{
	unsigned char address;
	if(y==1)
	         address=0x80+x;	 //显示在第一排的时候的x的地址 
	else
	         address=0xc0+x;	 //显示在第二排的时候的x的地址 
	LCD_write_command(address);	 //输入地址 
	LCD_write_data(dat+48);		 //输入数据 
}
void dis_num(void)
{
	unsigned char i=0,j=0,k=0;
	LCD_write_command(0x01);//清除屏幕显示
	character[0] = fre/10000000;
	character[1] = fre/1000000%10;
	character[2] = fre/100000%10;
	character[3] = fre/10000%10;
	character[4] = fre/1000%10;
	character[5] = fre/100%10;
	character[6] = fre/10%10;
	character[7] = fre%10;
    character[8] = 'H';
	character[9] = 'z';
	for(i = 0;i<4;i++)		 //显示“fre=”
	{
	 	LCD_disp_char(i+0,1,character_1[i]);
	}
	for(i = 0;i<10;i++)	 //判断第一个不为0的数
	{
		if(character[i]!=0)
			break;
	}
	k = 8-i;
	for(j = 0;j<k;j++)	 //显示所有的数字
	{
			LCD_disp_num(4+j,1,character[i++]);	
	}
    for(i = 5;i<7;i++)	 //显示“Hz”
	{
	 	LCD_disp_char(j+4,1,character_1[i]);
		j++;
	}
}
//----------------主函数--------------------
void main()
{ 
	unsigned char i;
	LCD_init();
	timer_init();             //定时/计数器初始化 
	for(i = 0;i<4;i++)
	{
	 	LCD_disp_char(i+0,1,character_1[i]);
	}
	while(1)
	{
		dis_num();         //显示
		delay_1s();
	}
}
//-------------------定时/计数器初始化--------------
void timer_init(void)         //定时/计数器初始化
{ 
	TMOD=0x66;                //计数器0和计数器1工作工作方式2，自动重装初值 
	TH0=0;                    //计数器初值为0
	TL0=0;
	TR0=1;                    //计数器开始计数	    
	ET0=1;                    //打开计数器0中断   
	TH1=0;                    //计数器初值为0
	TL1=0;
	TR1=1;                    //计数器开始计数	    
	ET1=1;                    //打开计数器1中断   
	RCAP2H=(65536-62500)/256; //在程序初始化的时候给RCAP2L和RCAP2H赋值， 
	RCAP2L=(65536-62500)%256; //TH2和TL2将会在中断产生时自动使TH2=RCAP2H,TL2=RCAP2L。 
	TH2=RCAP2H;               //12M晶振下每次中断62.5ms(1s=1000ms=62.5ms×16)
	TL2=RCAP2L;
	ET2=1;                    //打开定时器2中断	 
	TR2=1;                    //定时器2开始计时  
	EA=1;                     //开总中断   
} 
//------------------中断函数----------------------
void timer2(void) interrupt 5 //定时器2中断(62.5ms)
{
	time++;
	TF2=0;                    //定时器2的中断标志位TF2不能够由硬件清零，所以要在中断服务程序中将其清零
	if (time==16)             //定时1s时间到  
	{
	   time=0;                //计时清0
	   EA=0;                  //关中断		 
	   fre=(long)count1*256+TL1;     //count*256强制转换成long型，否则将不产生进位~先判断分频后(计数器1)
	   FLAG = 0; 
	  
	   if(fre<2000)//如果不到200KHz则读取分频前(计数器0)频率(200K÷100=2000)
	   {
	   		fre = (long)count*256+TL0;
			FLAG = 1;          
	   } 
		if(!FLAG)
		{
			fre = fre *100;//100分频
		}
	   TL0=0;                 //清零计数器0计数	    
	   TH0=0;
	   TL1=0;
	   TH1=0; 
	   count=0;               //清零计数器0计数	  
	   count1=0;
	   EA=1;                  //开中断	    
	}
} 
//----------------------------------------------------------------
void timer0(void) interrupt 1 //计数器0中断(100分频前)	 
{
	count++;
}		
//----------------------------------------------------------------
void timer1(void) interrupt 3 //计数器1中断(100分频后) 
{
	count1++;
}

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